The redistribution of arsenic in Si has been studied in terms of the relative rates of oxidation and diffusion in silicon. Redistribution of arsenic in silicon during oxidation is dependent on the ratio of oxidation rate to the diffusivity in silicon,B/D1/2, as well as on the thermodynamic equilibrium segregation coefficient. It was found that for the value ofB/D1/2larger than 50, most of the arsenic impurity becomes trapped in SiO2. For the smaller value ofB/D1/2, snowplowing of arsenic results.